Blends of polyestercarbonate with 4-methyl-1-pentene polymers

ABSTRACT

Polyestercarbonate compositions having superior environmental stress crack resistance are obtained by blending with up to about 12 weight percent of a polymer of 4-methyl-1-pentene.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Pat. No. 4548991,application Ser. No. 493,081, filed May 9, 1983.

BACKGROUND OF THE INVENTION

This invention relates to blends of an aromatic polyestercarbonate witha 4-methyl-1-pentene polymer.

Blends of polycarbonate with a variety of polyolefins are described inthe prior art. U.S. Pat. No. 3,431,224 discloses blends of polyethylene,polypropylene, polyisobutylene, a copolymer of ethylene and an alkylacrylate or a copolymer of ethylene and propylene. U.S. Pat. No.3,477,978 describes blends of an aromatic polycarbonate with a polymerof an olefin of 2-3 carbon atoms. Protective body armor fabricated froma polycarbonate and 3 to 7 percent of a polyolefin is claimed in U.S.Pat. No. 3,437,631. A process for preparing a blend of an olefin polymerand a polycarbonate is described in U.S. Pat. No. 3,801,673.

U.S. Pat. No. 4,245,058 teaches that ternary blends of aromaticpolycarbonates, an acrylate copolymer and a polyolefin are thermoplasticcompositions possessing improved impact strength. The polycarbonatesemployed in these blends also can contain ester moieties. The JapanesePatent Application No. 55-090,550, published July 9, 1980, alsodescribes blends of polyestercarbonates and certain polyolefins.

The prior art blends of polycarbonate and polyolefin exhibit someimprovement in impact strength relative to polycarbonate alone,particularly at below ambient temperatures or after exposure to hightemperatures. However, relatively little improvement is imparted bythese blends in the capacity of the thermoplastic to withstand exposureto organic solvents without failure under stress. This property isfrequently referred to as "environmental stress crack resistance". TheIzod impact strength of these blends also declines following extendedexposure to water. Accordingly, it would be desirable to identify blendsof aromatic ester carbonate polymers, which exhibit greaterenvironmental stress crack resistance, improved processability andimproved strength after exposure to water.

SUMMARY OF THE INVENTION

In accordance with the present invention, novel, normally-solid blendsof at least one aromatic ester carbonate polymer with from about 2 toabout 12 percent by weight of an addition polymer of 4-methyl-1-penteneper hundred parts of aromatic polycarbonate and polyestercarbonate aredisclosed. The polymer of 4-methyl-1-pentene can be a homopolymer or canbe prepared by addition polymerization of 4-methyl-1-pentene with up toabout 15 mole percent of some other alpha-olefin monomer. The term"normally-solid" is meant to denote that these blends are generallysolids at ambient temperatures in the absence of solvents.

The subject blends exhibit improved environmental stress crackresistance relative to aromatic ester carbonate polymer blends withhigh-density polyethylene containing the same percentage of polyolefin.This improvement is especially noticeable in the presence of gasoline orsolvents of similar composition. The subject blends also exhibit an Izodimpact strength of at least about 5.0 foot-pounds per inch notch whentested in accordance with ASTM D-256 after immersion in 100° C. waterfor 1000 hours.

Further, the subject blends exhibit higher melt flow and easierprocessability than the aromtic ester carbonate polymer. In a preferredembodiment of this invention, the blend exhibits a melt flow indexmeasured in accordance with ASTM Method No. D-3307 at least about 10percent higher than the aromatic ester carbonate polymer.

DETAILED DESCRIPTION OF THE INVENTION POLYMER OF 4-METHYL-1-PENTENE

Polymers of 4-methyl-1-pentene are well known in the prior art. U.S.Pat. Nos. 2,957,225, 3,969,333, 3,969,335 and 4,342,854 describe methodsof making such polymers and are incorporated herein by reference. Thesepolymers are also available commercially from Mitsui PetrochemicalIndustries, Ltd. These polymers are essentially linear and are preparedby predominantly 1,2-polymerization. In contrast, U.S. Pat. No.3,317,500 teaches a method of preparing a cross-linked polymer from4-methyl-1-pentene by predominantly 1,4-polymerization of the monomer,which is not desirable in the subject blends.

The polymers are advantageously essentially homopolymers, but minoramounts of other alpha-olefins having 2 to 12 carbons can also beemployed in preparing these polymers. Preferred comonomers arestraight-chain alpha-olefins having from 4 to 10 carbon atoms, morepreferably 5 to 7 carbon atoms. Any olefin present in addition to4-methyl-1-pentene should not be present in quantities whichsignificantly disrupt the crystallinity of the polyolfin, inasmuch as apolyolefin having a percent crystallinity of at least about 10 percent,more preferably at least about 30 percent, is preferred. The percentcrystallinity is conveniently determined by the use of X-ray diffractiontechniques known in the art.

In general, it is preferred for the polyolefin to contain at least 85mole percent moieties derived from 4-methyl-1-pentene, more preferablyat least about 90 mole percent, most preferably at least about 95 molepercent. In some embodiments it is desirable to copolymerize with aminor amount (about 2 to about 10 mole percent) of a C₄ to C₁₀alpha-olefin in order to reduce formation of voids, as described byClark and Palmer, The Chemistry of Polymerization Processes, MonographNo. 20, Society of the Chemical Industry, London, England, 1966, pp.82-103.

Polyestercarbonate

The aromatic polyestercarbonates (hereinafter, "ester carbonatepolymers") employed as components in the subject blends are compoundswell known in the prior art. Mixtures of two or more of these componentscan also be employed.

The ester carbonate polymers contain a plurality of repeating unitscorresponding to the formula I ##STR1## wherein each R is independentlyaromatic hydrocarbylene or inertly-substituted aromatic hydrocarbylene,each R' is independently meta- or para-phenylene and x is a numbergreater than 0 but less than about 10. Since x represents an averagevalue corresponding to ester moieties in the polymer composition andpolymer molecules generally vary in the number and ordering of suchunits, x need not be an integer.

For the purposes of this invention, an "aromatic hydrocarbylene"is adivalent radical containing at least one aromatic moiety. Preferably,two aromatic moieties are present and each aromatic moiety bears one ofthe valences. More preferably, the aromatic moieties are phenylene. Thetwo aromatic moieties can be linked by ##STR2## or a chemical bond.Preferably, the aromatic moieties are joined by an alkylene oralkylidene group optionally bearing a phenyl substituent. An "inertlysubstituted" group is one having one or more substituents other thanhydrogen, said substituents being inert in the blended composition andduring the preparation of the composition.

The aromatic ester carbonate polymer is conveniently prepared byreaction of a dihydric phenol with phosgene or a phosgene precursor anda diacid chloride. Preferred as dihydric phenols are bisphenol A,bis-(4-hydroxyphenyl)methane, 1,1-bis-(4-hydroxyphenyl)-ethane andphenolphthalein. Most preferred is bisphenol A.

A minor amount of a polyhydric phenol can also be employed to prepare abranched aromatic ester carbonate for use in this invention. See U.S.Pat. No. 4,001,184. The polycarbonate should not be highly cross-linked.However, generally it is preferred that the ester carbonate polymercomponent is essentially linear.

The polyestercarbonates which can be used herein can also be prepared bya variety of methods taught in the prior art. U.S. Pat. Nos. 4,260,731,4,255,556, 4,156,069 and 4,105,633 describe polyestercarbonatecopolymers and methods of making them and are incorporated herein byreference. U.S. Pat. No. 3,169,121 teaches a method for preparing ablock polyestercarbonate containing a preponderance of carbonatemoieties. Ordered polyestercarbonates are in general the preferredpolyestercarbonates for use in the subject blends. Particularlypreferred are the polyestercarbonates claimed in U.S. Pat. No.4,330,362.

The group represented by "R" in formula I is preferably derived from adihydric phenol, such as, for example, 2,2-bis-(4-hydroxyphenyl)propane(i.e., bisphenol A), bis-(4-hydroxyphenyl)methane,1,1-bis-(4-hydroxyphenyl)ethane and phenolphthalein. Most preferably,"R" is derived from bisphenol A. The preferred ratio of ester tocarbonate groups in the polyestercarbonate is from about 1:1 to about4:1.

Particularly preferred as a polyestercarbonate component of the blendare ordered copolymers made up of repeating units corresponding toformula I wherein the molar ratio of para-phenylene to meta-phenylene inthe groups represented by R' is in the range from 0.95:0.05 to 0.05:0.95and x is a number from 0.05 to 10. More preferably the molar ratio ofpara- to meta-phenylene is in the range from 0.9:0.1 to 0.5:0.5, mostpreferably about 0.8:0.2. The Izod impact resistance at ambienttemperatures (determined in accordance with ASTM D-256) and theprocessability of the blend generally increases with increasing amountsof meta-phenylene in the copolymer. The heat distortion, low temperatureimpact resistance and fatigue resistance generally increase as thepara-phenylene present in the copolymer increases, while notchsensitivity and thickness sensitivity generally decreases.

Polyestercarbonates having a weight average molecular weight of at least25,000 grams per mole, more preferably from about 28,000 to about33,000, are preferred. The molecular weight is conveniently determinedby gel permeation chromatography using a bisphenol-A polycarbonate forcalibration. Where an aromatic ester carbonate polymer having amolecular weight lower than about 25,000 is employed, the physicalproperties of the blend may be deleteriously affected.

More than one polyestercarbonate and mixtures thereof with polycarbonatecan be employed in the subject blends. Blends having a predominantamount of polycarbonate have been observed to undergo the greatestimprovement in properties on blending with the 4-methyl-1-pentenepolymer. Especially preferred as carbonate polymers are blends of apolycarbonate and polyestercarbonate having an overall ratio ofester-to-carbonate groups in the range from about 3:7 to about 1:2.

Other Components

Other components can be incorporated into the polymer blend to improvespecific properties of the blend. For example, fire retardants,plasticizers, mold release agents, thermal stabilizers and U.V. lightstabilizers can all be used to advantage. Generally, these othercomponents are used in small, but effective amounts so as to minimizedeleterious effects on the properties of the blend.

Blending

The components of the subject compositions can be blended by anytechnique which effects intimate intermixing of components withoutsignificant mechanical or thermal degradation of the polymer components.For example, the components can be dissolved or dispersed in acompatible diluent, blended together to produce a homogeneous dispersionor solution and the diluent removed.

The preferred method for blending the polymer components is in anextruder at a temperature and shear rate which will effect intimatemixing without significant polymer degradation. Generally, temperaturesin the range from about 250° to about 370° C. are suitable. An extrudertemperature of at least 285° C. is preferred when component polymershaving high softening temperatures are employed.

Properties

The blends of aromatic ester carbonate polymers with a polymer of4-methyl-1-pentene when compared with the ester carbonate polymer aloneexhibit improved Izod impact strength, particularly at subambienttemperatures, when a sharp notch is employed or after exposure totemperatures of about 100° C. for an extended period of time (i.e., heataging). The tensile strength and Vicat heat distortion of the blendtypically decrease with an increasing percentage of polyolefin. Thehydrolytic stability of an ester carbonate polymer containing thepoly(4-methyl-1-pentene) is superior to the ester carbonate polymeralone or one containing a like quantity of polyethylene. The improvementin hydrolytic stability is most prominent in water having a temperatureof at least about 90° C. The environmental stress crack resistance(ESCR) of the subject blends, especially in gasoline and similarsolvents, is also superior to the ester carbonate polymer and blendswith polyolefins known in the prior art. This improvement isparticularly noticeable at a tensile stress of at least about 2000 psi.

The subject blends containing a substantial quantity ofpolyestercarbonate, i.e., an overall ratio of ester to carbonatemoieties of at least 1:20, possess hydrolytic stability and ESCRsuperior to polycarbonate. Consequently, the improvement in propertiesattained by the addition of poly(4-methyl-1-pentene), thoughsignificant, is not as great as where less ester is present.

The polyestercarbonate blends exhibiting the best overall combination ofproperties are in general those containing from about 2 to about 10weight percent of a 4-methyl-1-pentene polymer, more preferably fromabout 3 to about 8 weight percent, most preferably about 4 to about 6weight percent.

The following examples are presented to illustrate the invention. Unlessotherwise indicated, all parts and percentages are by weight.

GENERAL PREPARATION OF BLENDS USED IN EXAMPLES

A bisphenol A polycarbonate sold by Mobay Chemical Company under thedesignation MERLON M50 polycarbonate was dry blended with a quantity ofpolyolefin to prepare a mixture containing a specific percentage ofpolyolefin. The resulting mixture was dried at 95° C. for 4 hours andextruded at a melt temperature of 275° C. using a two-stage,single-screw Killion extruder having a three-fourths inch screw diameterwith a length:diameter ratio of 24:1.

The extruded strand was pelletized and dried at 125° C. for four hours.The pellets were then injection molded at a melt temperature of 290° C.and a mold temperature of 65° C.

A polyestercarbonate (prepared as described in U.S. Pat. No. 4,330,662)was melt blended with the polycarbonate prior to dry blending with thepolyolefin. The polyestercarbonate component had an ester-to-carbonateratio of 3:1 and a ratio of para-phenylene to meta-phenylene moieties of4:1. The resulting polycarbonate/polyestercarbonate blend had an overallester-to-carbonate group ratio of 1:5.7.

EXAMPLES 1-3, COMPARATIVE EXPERIMENTS A-C

The hydrolytic stability of a blend of polycarbonate and apolyestercarbonate (ester-to-carbonate ratio=1:5.7) containing 2,5 or 10weight percent (PMP) of a 4-methyl-1-pentene polymer, sold by MitsuiPetrochemical under the designation DX-810, was tested for hydrolyticstability in refluxing water. Periodically specimens were removed fromthe water and the specimens were notched (7.5 mm notch radius). The Izodimpact strength (in foot-pounds/inch) of the notched specimens was thendetermined in accordance with ASTM D-256-81, a standard test methodpromulgated by the American Society for Testing Materials. Comparativeexperiments were conducted with polycarbonate/polyestercarbonate blendalone, as well as with HDPE and polypropylene. The results are tabulatedin Table I.

The blends containing PMP exhibited unexpected hydrolytic stability whencompared with the polycarbonate/polyestercarbonate alone, as well asblends with polypropylene or HDPE.

                  TABLE I                                                         ______________________________________                                        Izod Impact Strength                                                          Polyolefin    Hours Water Immersion                                           (Wt. %)       0      100    250   500  1000 1500                              ______________________________________                                        Example                                                                       1      PMP (2%)   12.8   *    11.2  11.8 6.8  *                               2      PMP (5%)   13.0   11.1 13.0  10.5 13.0 8.7                             3      PMP (10%)   9.5   *     8.3   8.0 7.1  *                               Comp.                                                                         Exp.**                                                                        A      None       17.1   2.2  *     *    *    *                               B      HDPE (5%)  12.6   9.9   8.5   5.4 1.3  *                               C      PP (5%)    11.7   *    10.3  *    6.7  2.9                             ______________________________________                                         *No impact strength determined.                                               **Not embodiments of this invention.                                     

EXAMPLE 4, COMPARATIVE EXPERIMENTS D-F

The environmental stress crack resistance of compositions identical tothose immersed in refluxing water and tested for hydrolytic stability inExample 2 and Comparative Experiments A, B and C are tested to determineenvironmental stress crack resistance. The environmental stress crackresistance (ESCR) of the resins was measured using the techniquedescribed by R. A. Bubeck et al, Poly. Eng. Sci., 21, 624 (1981). Aninjection molded specimen 0.125 inch thick×0.500 inch wide×4.0 incheslong with a curved stress concentrator milled into it (6.4 mm radius) oneach side and directly opposite one another was mounted in anenvironmental containment fixture and a tensile load of 2000, 2500 or3000 psi (pounds per square inch) was applied after the solvent mixturewas introduced into the containment fixture. A solvent mixture of 75vol. percent isooctane and 25 vol. percent toluene was used. The resultsare tabulated in Table II. The environmental stress crack resistance ofthe subject blends is consistently superior to that of the blends testedfor comparison.

                  TABLE II                                                        ______________________________________                                                            Minutes to Failure                                                            at Given Stress (psi)                                              Polyolefin (Wt. %)                                                                         2000    2500   3000                                     ______________________________________                                        Example                                                                       4          PMP (5%)       414     80   26                                     Comp. Exp.**                                                                  D          None            90     31   13                                     E          HDPE (5%)      108     24   14                                     F          PP (5%)        235     37   19                                     ______________________________________                                         **Not embodiments of the invention.                                      

EXAMPLES 5-7, COMPARATIVE EXPERIMENTS G-I

The Izod impact strength and tensile strength of melt-blendedpolycarbonate/polyestercarbonate (ester-to-carbonate group ratio 1:5.7)blended with PMP was tested in accordance with ASTM-256-81 at 23° and-30° C. using a 10 mil notch radius. Tensile strengths at yield weredetermined for samples of the same composition using methods describedin ASTM D-638. Tests of comparative blends were also conducted. Theresults are compiled in Table III.

                  TABLE III                                                       ______________________________________                                                    Izod Impact  Tensiles at Yield                                    Polyolefin    Strength      Stress   Strain                                   (Wt. %)       23° C.                                                                          -30° C.                                                                         (psi)  (%)                                    ______________________________________                                        Example                                                                       5      PMP (2%)   12.8     7.1    8620   6.5                                  6      PMP (5%)   13.0     10.1   7980   6.1                                  7      PMP (10%)   9.5     7.6    7680   5.6                                  Comp.                                                                         Exp.**                                                                        G      None       17.1     12.7   8630   6.2                                  H      HDPE (5%)  12.6     9.4    8080   6.6                                  I      PP (5%)    11.7     7.4    8140   6.4                                  ______________________________________                                         **Not embodiments of the invention.                                      

What is claimed is:
 1. A normally solid blend of at least one aromaticester carbonate polymer and at least one polycarbonate resin with apolyolefin comprising about 2 to about 12 percent by weight of anaddition polymer of 4-methyl-1-pentene per hundred parts of aromaticester carbonate polymer and polycarbonate resin, said addition polymerbeing prepared by the homopolymerization of 4-methyl-1-pentene or bycopolymerization of 4-methyl-1-pentene with up to about 15 mole percentof other olefin monomers, said aromatic ester carbonate having a weightaverage molecular weight of at least 25,000 grams per mole and an esterto carbonate ratio of about 4:1 or less, with the proviso that theresulting blend exhibits an Izod impact strength of at least about 5.0foot-pounds per inch notch when tested in accordance with ASTM D-256following immersion in 100° C. water for 1000 hours and has an overallratio of ester-to-carbonate groups in the range from about 1:9 to about1:2.
 2. The blend as described in Claim 1 wherein the aromatic estercarbonate polymer contains a plurality of repeating units correspondingto the formula ##STR3## wherein each R is independently aromatichydrocarbylene or inertly substituted aromatic hydrocarbylene, each R'is independently meta- or para-phenylene and x is a number greater than0 but less than about
 10. 3. The blend as described in claim 2 whereinthe aromatic ester carbonate polymer is derived from bisphenol A,bis-(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane orphenolphthalein.
 4. The blend as described in claim 3 wherein thearomatic ester carbonate polymer is derived from bisphenol A.
 5. Theblend as described in claim 3 wherein the addition polymer of4-methyl-1-pentene is made from no more than 10 weight percent of otherolefin monomers.
 6. The blend as described in claim 5 wherein thearomatic ester carbonate polymer is derived from bisphenol-A.
 7. Theblend as described in claim 5 wherein the blend exhibits a melt flowindex at least about 10 percent greater than the aromatic estercarbonate polymer alone.